This highly integrated PWM controller provides several features to enhance the performance of low-power flyback converters. To minimize standby power consumption, the proprietary green-mode function provides off-time modulation to linearly decrease the switching frequency under light-load and zero-load conditions. This green-mode function enables the power supply to meet international power conservation requirements. The supply voltage, V_DD, is also used for feedback compensation, to regulate the output voltage without requiring a conventional TL431 and a photo-coupler. The typical start-up current is only 8µA, while the typical operating current can be as low as 3.6mA. A large start-up resistance could be used to achieve even higher power conversion efficiency. SGP400 integrates a frequency hopping function, which helps reduce EMI emission of a power supply with minimum line filters. Built-in synchronized slope compensation maintains the stability of peak current-mode control. Proprietary internal compensation ensures constant output power limiting over a universal range of AC input voltages, from 90V_AC to 264V_AC. Pulse-by-pulse current limiting ensures a constant output current, even if a short-circuit occurs. Also, the internal protection circuit disables PWM output if V_DD exceeds 22.7V. The gate output is clamped at 16.7V to protect the power MOS from over-voltage damage. The built-in over temperature protection (OTP) function shuts down the controller at 140°C with a 30°C hysteresis. The SGP400, designed to provide a low-cost total solution for flyback converters, is available in a small footprint, 6-pin, SOT-26 package.

• Linearly decreasing PWM frequency
• Green-mode under light-load and zero-load conditions
• Constant voltage (CV) and constant current (CC)
• No secondary feedback
• Low start-up current (8µA)
• Low operating current (3.6mA)
• Leading-edge blanking
• Constant power limit
• Universal AC input range
• Synchronized slope compensation
• 140°C OTP sensor with hysteresis
• V_DD over-voltage clamping
• Cycle-by-cycle current limiting
• Under-voltage lockout (UVLO)
• Fixed PWM frequency with hopping
• Gate output maximum voltage clamped at 17V
• Small SOT-26 package

Low-power flyback power converters, such as:

• Battery chargers for cellular phones, cordless phones, PDAs, digital cameras, and power tools
• Power adapters for ink jet printers, video game consoles, and portable audio players
• Open-frame SMPS for TV/DVD standby and other auxiliary supplies, home appliances, consumer electronics, and PC 5V standby-power
• Replacements for linear transformers and RCC SMPS